Okay, so this might be a dumb question, but can someone help me understand how bots utilizing the Andymark Climber in a Box would be able to stay hanging after the match ends? The kit doesn’t seem to include any sort of ratchet or anything, so is it simply a high gear ratio on the gearbox that’s preventing the spool from unwinding after the match ends, or am I missing something?
We didn’t buy the kit but my team is modeling our climbers to be very similar to the Climber in a Box design, and we’re currently thinking that we’ll need a releasable ratchet of some kind, but maybe there’s a way to avoid that since the climber in a box kit doesn’t seem to include a ratchet? I don’t want our climber to end up being more complicated than it needs to be! The less points of failure the better
The AndyMark Climber in a Box does not include a motor or gearbox, but is compatible with many off-the-shelf planetary gearboxes on the market that have a 2" bolt circle mounting pattern and support a 2" long 1/2" hex output shaft, including the highly durable blue Sport Gearboxes when a 2" replacement shaft is purchased.
So, anyone utilizing the Climber in a Box needs to pick their own gearbox. Some gearboxes may be able to hold the robot by themselves, but that is going to be highly dependent on what you pick. Instead, i would look at including a some type of break on it. The ratchet slice available for the VersaPlanetary is pretty nice, it’s what we’re going to be using (with the Thriftybot climber, but it’s pretty much the same thing as the AndyMark one, mechanically speaking), but it’s not the only solution available!
@Jon_Stratis Okay, makes sense. I have looked into that ratchet slice you mentioned, but I was under the impression that it isn’t releasable/deployable and that it’s always restricting rotation in one direction, is that not the case? Because to climb the winch spool would have to be unwound, then wound up, and then ratcheted to prevent it from unwinding, so the ratchet can’t be active until after that initial unwinding to raise the hook
The ratchet can be released manually by pressing the “button” outlined in blue below, or pulling on the “hole” outlined in red below. So releasing it can take some engineering work, to get a mechanism (like a pneumatic piston or linear servo) in the right place and pulling/pushing with the right amount of force. You can reduce the amount of force needed by pulling down on your hooks a little when trying to release the ratchet.
Okay, interesting, so essentially it can be used as a “releasable” ratchet by pulling/pushing that red-outlined hole with a pneumatic piston? That might be worth looking into for us
But, just to play devil’s advocate, would it be reasonably-achievable to hold a hang without any sort of ratchet? We plan to use 2 climbing hooks instead of just 1 which should theoretically make that even easier, if we have a high-enough gear ratio could it work reliably?
It’s entirely possible. Keep in mind, however, that the higher your gear ratio, the slower the climber moves. It’s a tradeoff. I was intrigued by this post a while back, you may find it informative!
For the application the OP, @Isopod00, has in mind, they may want to make it release through a manually operated mechanism that is used when removing the robot from the rungs after the end of the match.
True, but it’s also very useful to be able to deploy the hooks a second time if you missed the climb the first try, so being able to actuate it during the match is a good idea
You would only get one chance, but you could just wind up the rope backwards for the start of the match. Then, going forward unspools the rope until it’s fully extended, then as you continue, it pulls back in.
Yes. That is a nice option to have. It all depends on finding a suitable ratchet mechanism first. The way the ratchet is actuated is a separate decision based on choosing between more functionality with some extra complexity and less functionality and a somewhat simpler mechanism.
We plan to have 2 Climber-in-a-Box style climbing hooks both with a 775pro on a 100:1 gear reduction. In the past, we’ve used a single hook with a 100:1 775pro and have needed a ratchet, but now that we’re using 2 hooks I think we’re just going to try it without any sort of ratchet first, and then if the friction of the gearboxes isn’t enough to hold us up we will add a ratcheting mechanism of some kind. The reason why I’m trying to outright avoid a ratcheting system if we can is purely for space/weight/simplicity sake, but if we end up needing to use one then we will
You only have to stay up for 5 seconds - the brake mode on a brushless motor is very strong. Quite possible that this may not be nearly as much of a problem as it has been historically - worth checking on.
Other than ratchets, some teams have used pneumatic actuators to “lock” their tube into place by engaging with holes or other features in multiple stages of tubing. These are nice because they allow you to reverse the mechanism before climbing, and if you use a single solenoid you can have the cylinder auto-fire when the robot disables just to be safe.
